The present invention relates to a light or transparency adapter for image scanners and in particular to a light for scanning transparencies for general use with any flat bed type or hand held type of image scanner and the resulting combination of this transparency adapter and a scanner of any type. The present invention also relates to a method of lighting transparencies for scanning.
Flat bed image scanners are widely used to electronically read full page or smaller images and text, formed on paper-like and film-like media. Flat bed scanners have motor driven, traversing, linear optical sensing heads to provide a uniform scan. These have largely displaced narrow, hand held scanners which are smaller by design, require steady hand movement and are usually equipped with non-standardized electronic interfaces.
The typical flat bed scanner is a box style device with a clear glass top image window designed to accept the original media to be scanned and subsequently electronically copied. These units tend to have industry standardized electronic interfaces to allow easy connection to such items as personal computers. Inside and beneath the clear glass top of the flat bed scanner is a transversing linear array optical sensing head, usually close-coupled to its own light source so as to illuminate, by reflection. This is the way the scanner reads opaque media, such as printed paper or photographs, placed image-side down on the glass top window of the scanner.
Transparent media such as photographic negatives, or slides, transparencies, x-rays, etc. require transmitted illumination for scanning and cannot use reflective light sources only to obtain desirable results. The typical close-coupled light sources within flatbed scanners are inadequate. Conventional additional attachments designed to provide overhead transmitted light in conjunction with or in synchronization with the transversing optical sensing head are available, but are complicated and expensive for the occasional or home user. These attachments tend to be customized for the specific flatbed scanner in use. A major concern is providing uniform, transmitted lighting through the transparent media during the scanning and to do so simply and inexpensively.
One such adapter for use on a flat bed scanner to scan transparencies is disclosed in U.S. Pat. No. 5,467,172. This patent discloses a rectangular box with a light module having two linear tubular florescent bulbs and with two light diffuser plates and a lighting guide located between the bulbs and the transparency to be scanned. The light source is on both sides of the transparency adapter, and many parts are required to try to get uniform light to the object to be scanned. This reference neither discloses nor suggests the present invention.
Another means for back lighting a scanner to enable it to scan x-rays, etc. is disclosed in U.S. Pat. No. 5,430,289. The device disclosed in this patent is a scanner lid having a light source built in containing at least one fluorescent linear tube bulb. This reference acknowledges the variations in light intensity such a light source produces and the reduced quality of the transparency scan that this variation causes. This reference discloses apparatus for compensating or correcting this variation by adding several pieces of expensive equipment including a sensor to measure the light intensity and to convert the actual light intensity into an electrical signal and a second controller to control the lamp intensity. This solution and device is impractical or very expensive for the occasional and/or home users.
Hand held scanners suffer from the same problems, but with the geometry reversed. Inside the hand held scanner is a fixed linear optical array sensing head with a close-coupled reflective light source. The opaque media is usually placed image side up, on a flat surface and the hand held scanner is manually moved across the medians surface. A light source for allowing scanning of transparencies on a hand held scanner is disclosed in U.S. Pat. No. 5,282,081. The device disclosed there includes a single fluorescent linear tube lamp, reflective mirror, a lens and numerous other elements which must work in concert to achieve a uniform light intensity, all of which make the device very expensive and complex for the occasional and/or home user.
A still different device for use in scanning transparencies and for compensating for different intensities of light striking different parts of the transparency is disclosed in U.S. Pat. No. 4,568,984. This complex solution simultaneously performs opaque and transparent master scanning to generate scanning signals for each point on the transparency and to eliminate amplitude errors in the transparency scan by combining the recognition signal with the actual image signal. This again is a complex and relatively expensive solution for the occasional and/or home user.
Another converter for allowing a normal reflective scanner to also scan transparencies like x-ray film is disclosed in U.S. Pat. No. 5,381,245. This conversion requires a linear lamp and a lamp support to be attached to the scanners traversing assembly in some undisclosed manner and the use of various transparent and white opaque calibration strips and means for converting light passing through one of the calibration strips into a digital signal. This conversion device would be too expensive and too difficult to attach to the typical scanner to be practical for scanning transparencies by the occasional and/or home user.
Another converter for allowing a typical reflective scanner to also scan transparencies is disclosed in U.S. Pat. No. 5,483,356. This converter comprises a housing with one or more linear light bulbs mounted therein and a light transmitter plate with a protective layer on an exposed side. This reference acknowledges that the uniformity of the light passing through the transparency can be made more uniform and brighter by using two or more linear light bulbs in the housing instead of only one. Aside from requiring two or more bulbs for good uniformity, the light transmitter must be a special material such as some undisclosed kind of polycarbonate material of some undisclosed thickness. Even if this converter works well, it suffers from a nonuniform light source and it is more expensive and more complicated than desired.
Attempting to get a more uniform light source, a transparency adapter disclosed in U.S. Pat. No. 5,652,665 uses an oval shaped refractor and a refractor plate with a hot cathode-ray tube light source. Aside from these relatively expensive items, a traversing mechanism is required to move this light source across the transparency for scanning. Consequently, this adapter would be very expensive for the occasional user and/or home transparency scanner.
Flat bed image scanners, once confined to the industrial and professional fields, have recently gained in general popularity because of lowered prices, effectively displacing the previously cheaper hand held scanners, but today's scanners are still hampered by not having an inexpensive, simple light assembly for scanning transparencies. There are specialty scanners which will only scan negatives and slides, to address this need, but especially for home and occasional use on transparencies, it is desirable to have a universal adapter, that is simple in design and cost effective, that can be used in with any typical flat bed scanner to scan transparent media.
Light fixtures for using round, ring shaped flourescent bulbs are known, but these are made to be permanently affixed to a ceiling or the like and they are not only different from the present invention, but would not be suitable for use in place of the present invention. It is also known to use a round flourescent bulb to surround and light a magnifying glass for bench work and other type of work such as microsurgery as disclosed in U.S. Pat. No. 5,312,393, but these devices are substantially different than the present invention and would be unsuitable to use as a transparency adaptor.